Paracoccus martensii, saline-alkaline tolerant growth-promoting microbial inoculum and application thereof

Abstract

The invention discloses paracoccus martensii, a saline-alkaline tolerant growth-promoting microbial agent and application thereof, and belongs to the technical field of microorganisms. The paracoccus martensii CZJ5 capable of promoting the plant growth and improving the salt stress resistance of the plant is screened out, and is preserved in the China General Microbiological Culture Collection Center (CGMCC), and the preservation number is CGMCC No.36255. Experimental results show that the paracoccus martensii CZJ5 has the salt-tolerant characteristic and the functions of nitrogen fixation, phosphorus dissolution, silicate removal, siderophore production and the like, and can effectively promote absorption and utilization of plants to elements such as nitrogen, phosphorus and iron, so that plant growth is promoted. The Paracoccus martensii CZJ5 has an obvious improvement effect on the growth of wild barley plants under salt stress and the salt stress tolerance of the wild barley plants. The invention provides a new growth-promoting bacterium for improving the salt tolerance of plants, and provides a new technical means for planting crops in saline-alkali soil.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of microbial technology, in particular to a Paraccoccus marcus, a salt-tolerant and alkali-tolerant growth-promoting microbial agent and application thereof. BACKGROUND

[0002] The soil salinity in agricultural soil refers to the presence of high concentration of soluble salt in the root soil water, and the high osmotic pressure formed by the soluble salt further limits the water absorption of plants and the balanced absorption of essential nutrient ions by roots to affect plant growth. The formation of saline-alkali land is the result of the joint action of multiple factors, common of which are long-term over-farming leading to soil structure destruction, excessive fertilization causing salt accumulation in soil, and water shortage and drought causing underground salt to rise to the surface with water evaporation, etc. The most direct impact of soil salinization is the reduction of grain yield, and the crop yield reduction caused by salinization every year poses a threat to food security. Improving and reasonably utilizing the salinized land not only can turn the originally low-yield "stiff soil" into arable land, but also can directly increase the land area for cultivation, which is of great significance to guarantee food supply stability and maintain ecological environment safety.

[0003] The beneficial microbial flora contained in the microbial agent can convert the substances in the soil into various nutrient elements through a series of decomposition and synthesis such as nitrogen fixation and phosphorus solubilization, improve soil fertility, and promote plant growth; the beneficial microorganisms can secrete various antibiotics and other antibacterial substances to inhibit the growth and reproduction of pathogenic bacteria, induce plant systemic disease resistance, reduce the occurrence of diseases, and improve plant stress resistance. In recent years, the application of microbial technology in the remediation of saline-alkali soil has been valued and strengthened, and mainly focuses on the research of microbial enhancement of plant salt-tolerance. It has been found that salt-tolerant microorganisms can improve the rhizosphere environment of plants, reduce the inhibition of salt on crop growth, and achieve the purpose of improving saline-alkali soil. It has been found that the strain can promote the emergence rate of mung bean, increase the biomass, and reduce the incidence under NaCl stress. It can be seen that the action of microorganisms can improve the survival rate and preservation rate of vegetation in saline-alkali soil to a certain extent, and plays an important role in long-term improvement of saline-alkali soil to restore soil physical and chemical properties and reconstruct the ecological environment of saline-alkali soil. SUMMARY

[0004] The present application provides a Paraccoccus marcus, a salt-tolerant and alkali-tolerant growth-promoting microbial agent and application thereof to solve the problems in the prior art. The Paraccoccus marcus CZJ5 has obvious promoting effect on the growth of wild barley plants under salt stress and the salt-tolerance of wild barley plants, and provides a new growth-promoting microbial agent for improving plant salt-tolerance and a new technical means for crop planting in saline-alkali land.

[0005] To achieve the above-mentioned purpose, the present application provides the following solutions.

[0006] The application provides Paracoccus marcusii CZJ5 which has been preserved in the China General Microbiological Culture Collection Center, and has a preservation number of CGMCC No. 36255, a preservation date of October 20, 2025, and a preservation address of No. 1, Xiliujiaoyi, Beichenxili, Chaoyang District, Beijing, China.

[0007] The application also provides application of the Paracoccus marcusii CZJ5 in preparation of a growth-promoting microbial agent for improving salt stress resistance of plants.

[0008] The application also provides a growth-promoting microbial agent, wherein the Paracoccus marcusii CZJ5 is used as an effective component.

[0009] Further, the growth-promoting microbial agent has an absorbance value of not less than 0.6 at a wavelength of 600 nm.

[0010] The application also provides application of the Paracoccus marcusii CZJ5 or the growth-promoting microbial agent in any one of the following:

[0011] (1) dissolving silicate;

[0012] (2) producing siderophores.

[0013] The application also provides application of the Paracoccus marcusii CZJ5 or the growth-promoting microbial agent in promoting plant growth.

[0014] The application also provides a method for promoting plant growth, which comprises the step of applying the Paracoccus marcusii CZJ5 or the growth-promoting microbial agent to a plant growth environment.

[0015] The application also provides application of the Paracoccus marcusii CZJ5 or the growth-promoting microbial agent in improving salt stress resistance of plants.

[0016] The application also provides a method for improving salt stress resistance of plants, which comprises the step of applying the Paracoccus marcusii CZJ5 or the growth-promoting microbial agent to a plant growth environment.

[0017] Further, the plant growth environment is a salt-containing environment.

[0018] The application discloses the following technical effects:

[0019] The application screens a Paracoccus marcusii CZJ5 which promotes plant growth and improves the salt stress resistance of plants. The Paracoccus marcusii CZJ5 is preserved in the China General Microbiological Culture Collection Center, and the preservation number is CGMCC No. 36255. Experimental results show that the Paracoccus marcusii CZJ5 has salt tolerance, nitrogen fixation, phosphorus dissolution, silicate dissolution and iron carrier production functions, can effectively promote the absorption and utilization of nitrogen, phosphorus, iron and other elements by plants, and further promote the growth of plants. The Paracoccus marcusii CZJ5 has obvious promotion effect on the growth of wild barley plants under salt stress and the salt stress resistance of wild barley plants. The application provides a new growth promoting bacteria for improving the salt tolerance of plants, and provides a new technical means for crop planting in saline-alkali soil. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description only constitute some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor on the basis of these drawings.

[0021] Figure 1 It is a colony morphology diagram of the Paracoccus marcusii CZJ5;

[0022] Figure 2 It is a phylogenetic tree diagram of the Paracoccus marcusii CZJ5;

[0023] Figure 3 It is a growth curve diagram of the Paracoccus marcusii CZJ5 in different salt concentrations;

[0024] Figure 4 It is a plate dissolution circle of the Paracoccus marcusii CZJ5 for dissolving phosphorus;

[0025] Figure 5 It is a plate dissolution circle of the Paracoccus marcusii CZJ5 for dissolving silicate;

[0026] Figure 6 It is a plate dissolution circle of the Paracoccus marcusii CZJ5 for producing iron carrier;

[0027] Figure 7 It is a phenotype observation result diagram of the Paracoccus marcusii CZJ5 for affecting the growth of wild barley in saline-alkali environment or non-saline-alkali environment;

[0028] Figure 8 It is a result statistical diagram of the Paracoccus marcusii CZJ5 for affecting the plant height, root length, dry weight and fresh weight of wild barley in saline-alkali environment or non-saline-alkali environment.

[0029] Depository information: Paracoccus marcusii CZJ5 has been deposited with the China General Microbiological Culture Collection Center (CGMCC) on October 20, 2025, and has been assigned accession number CGMCC No. 36255, and the deposit address is No. 1 Yard 3, Beichen West Road, Chaoyang District, Beijing, China Institute of Microbiology, Chinese Academy of Sciences. DETAILED DESCRIPTION

[0030] The various illustrative embodiments of the present application will now be described in detail below. The detailed description is made with reference to the accompanying drawings, wherein like reference numerals refer to like elements throughout the various figures. The present application is described with reference to the following examples.

[0031] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. In addition, for a range of values of, for example, a parameter, an intermediate value of the parameter is encompassed if the parameter is not limited to a specific value. Any intermediate value of a parameter, as well as any other stated or intervening value of that parameter, is encompassed within the scope of the present application. The upper and lower limits of these smaller ranges can independently be included or excluded in the range.

[0032] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Although preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application. All documents mentioned herein are incorporated by reference to disclose and describe the methods and / or materials in connection with which the documents are cited. In case of conflict, the content of the present specification will control.

[0033] Various modifications and changes can be made to the specific embodiments of the present application described herein without departing from the scope or spirit of the application. Other embodiments of the application will be apparent to those of ordinary skill in the art from the description and examples presented herein. The description and examples are illustrative of the application and are not intended to limit the scope of the application.

[0034] As used herein, the terms "comprises", "comprising", "includes", "including", "has", "having", "contains", "containing", or variations thereof, are intended to be open-ended terms that mean including, but not limited to.

[0035] LB solid medium: tryptone 10 g / L, yeast extract 5 g / L, sodium chloride 10 g / L, agar 18 g / L, pH adjusted to 7.0-7.2.

[0036] LB liquid medium: yeast extract 5 g / L, tryptone 10 g / L, NaCl 10 g / L, pH adjusted to 7.

[0037] Nitrogen-fixing medium (nitrogen-free medium): mannitol 10.0 g / L, CaCO3 5 g / L, KH2PO4 0.2 g / L, MgSO4·7H2O 0.2 g / L, NaCl 0.2 g / L, CaSO4·2H2O 0.2 g / L, agar 20 g / L, pH adjusted to 7.0-7.2.

[0038] Mengqinna organic phosphorus solid medium: glucose 10.0 g / L, yeast extract powder 0.4 g / L, (NH4)2SO4 0.5 g / L, MnSO4·4H2O 0.03 g / L, KCl 0.3 g / L, FeSO4·7H2O 0.03 g / L, NaCl 0.3 g / L, CaCO3 5 g / L, egg yolk lecithin 0.2 g / L, agar 20 g / L, pH adjusted to 7.0.

[0039] Silicate-lysing bacteria medium: sucrose 5.0 g / L, MgSO4 0.5 g / L, CaCO3 0.1 g / L, Na2HPO4 2.0 g / L, FeCl3 0.005 g / L, glass powder 1.0 g / L, agar 15.0 g / L, pH adjusted to 7.0-7.2.

[0040] CAS detection medium: chrome azurol S (CAS) 60.5 mg / L, cetyltrimethylammonium bromide 72.9 mg / L, FeCl3·6H2O 2.645 mg / L, NaH2PO4·2H2O 295.25 mg / L, Na2HPO4·12H2O 1213.5 mg / L, NH4Cl 125.0 mg / L, KH2PO4 37.5 mg / L, NaCl 62.5 mg / L, agar 9000.0 mg / L, pH adjusted to 6.7-6.9.

[0041] Example 1 Isolation and identification of growth-promoting bacteria strains

[0042] 1. Sample collection

[0043] Soil samples were collected from saline-alkali soil in Linze County, Zhangye City, Gansu Province; soil collection used five-point sampling method, in the selected area, five sampling points were determined, different degrees of saline-alkali soil were selected, 10-20 cm soil was collected, equal amount of soil was collected at each point, mixed and sealed in a sterile bag, and key information such as collection number, collection site and date was marked, and brought back to the laboratory for 4℃ low temperature preservation.

[0044] 2. Soil sample enrichment treatment

[0045] The soil sample was sieved through a 20 mesh sample sieve (pore size about 1 mm); 10 g of the sample to be tested was weighed into a triangular flask containing 90 mL of sterile aqueous solution (10-15 sterilized glass beads were placed in the flask), and was shaken at 28°C and 150 rpm for 2-3 h, and was allowed to stand for 10 min, to obtain a 10-fold diluted soil suspension, which was taken as 10 -1 diluted solution. 1 mL of the 10 -1 fold diluted solution was taken with a pipette and added to a test tube containing 9 mL of sterile water, and was blown and sucked to make a 10 -2 fold diluted solution, and the 10 -3 fold diluted solution was diluted in the same way to make 10 -4 fold, 10 -5 fold, 10 -6 fold, and 10 -7 fold serial gradient diluted solutions. 0.1 mL of each gradient diluted solution was uniformly spread on LB culture medium plates, and each concentration was repeated 3 times, and the plates were incubated in a 28°C constant temperature incubator for 2-3 d.

[0046] 3. Strain separation and screening

[0047] A plate with a suitable growth density of colonies (30-300 / plate) was selected, and different types of single colonies on the above LB culture medium plate were picked and streaked on LB culture medium plates, and were incubated at 28°C for 2-3 d. Single cells were picked again and streaked, and after 2-3 times of single cell streaking, single cell pure cultures of each strain were obtained. The single cells of each strain were picked and inoculated in LB liquid medium, and were incubated at 28°C and 150 rpm for 12-24 h, and strains with obvious growth in the medium were selected and purified for preservation.

[0048] 4. Strain purification and preservation

[0049] The pure strain was preserved at low temperature by freezing with 30% glycerol. The preserved strain was named L172.

[0050] Example 2 Morphological identification of the growth promoting bacterial strain

[0051] The purified strain L172 was picked and streaked on LB solid medium, and was incubated at 28°C for 2 d. Then the colony morphology was observed, and the colony morphology of the growth promoting bacteria is shown in Figure 1 .

[0052] The colony of the growth promoting bacterial strain L172 was smooth, with neat edges, slightly convex, and produced a luster.

[0053] Example 3 Molecular biological identification and preservation of the growth promoting bacterial strain

[0054] The isolated and purified strain L172 was subjected to molecular biological identification. DNA extraction, PCR amplification, and 16S rRNA gene sequencing were performed.

[0055] Forward primer 27F: 5'-AGAGTTTGATCCTGGCTCAG-3', SEQ ID NO. 1;

[0056] Reverse primer 1492R: 5'-TACGGCTACCTTACGACTT-3', SEQ ID NO. 2.

[0057] The amplified 16S rRNA PCR product was sent to Shengong Bioengineering (Shanghai) Co., Ltd. for sequencing.

[0058] Through homology comparison (Blastn) of nucleic acid sequences in the GenBank database on NCBI, strain L172 was preliminarily identified as Paracoccus sp.

[0059] The phylogenetic tree comparison result showed that strain L172 was relatively close to multiple species of Paracoccus sp. in evolutionary relationship, especially Paracoccus marcusii, which further verified the preliminary identification result based on 16S rRNA gene sequencing and homology comparison, i.e., strain L172 belonged to Paracoccus marcusii of Paracoccus sp., which provided important taxonomic basis for further research and application development of the strain, such as Figure 2

[0060] Paracoccus marcusii L172 was renamed as CZJ5. Paracoccus marcusii CZJ5 has been preserved in the China General Microbiological Culture Collection Center (CGMCC), with a preservation number of CGMCC No. 36255, a preservation date of October 20, 2025, and a preservation address of No. 3, Institute of Microbiology, Chinese Academy of Sciences, Beijing City, Chaoyang District, Beichen West Road 1st Courtyard 3rd.

[0061] Example 4: Salt tolerance of Paracoccus marcusii CZJ5

[0062] Preparation of seed solution: a single colony of Paracoccus marcusii CZJ5 was inoculated into an LB liquid medium test tube, cultured at 28°C, 180 rpm for 24 h, and a seed solution was prepared.

[0063] ​Prepare saline-alkali culture medium containing 0 mmol / L, 200 mmol / L, 400 mmol / L, 600 mmol / L and 800 mmol / L of salt, respectively, inoculate the seed liquid of Paracoccus marcusii CZJ5 with a 3% inoculation amount, cultivate for 40 h, and determine the growth curve of Paracoccus marcusii CZJ5 in different salt concentrations.

[0064] The growth curve is shown in Figure 3 As shown in Figure 3 It can be seen that: with the increase of the salt concentration in the culture solution, the time required for Paracoccus marcusii CZJ5 to enter the logarithmic phase is longer; the growth of the CZJ5 strain is best in 200 mmol / L salt concentration, and it enters the logarithmic phase after 2 h of cultivation and reaches the highest phase after 24 h; the CZJ5 strain can tolerate 400 mmol / L of salt concentration, and when cultivated in 400 mmol / L salt concentration, the OD 600 value of the bacterial concentration reaches more than 0.6 when it reaches the stationary phase, and it can be seen that Paracoccus marcusii CZJ5 can grow normally in a culture solution with a salt concentration of not more than 400 mmol / L, can maintain stable activity and tolerance, and Paracoccus marcusii CZJ5 can also grow in 600 mmol / L and 800 mmol / L gradients, so Paracoccus marcusii CZJ5 can grow and reproduce normally in a high-salt-concentration culture solution and maintain activity, which shows that Paracoccus marcusii CZJ5 can adapt to a high-salt-high-osmotic-pressure environment, has a wider application scenario, and can be used for biological treatment of high-salt wastewater and soil improvement of saline-alkali land, etc.

[0065] Example 5: Nitrogen fixation, phosphorus dissolution, silicate dissolution and siderophore production characteristics of Paracoccus marcusii CZJ5

[0066] 1. Nitrogen fixation detection experiment

[0067] Nitrogen-free medium detection: a little Paracoccus marcusii CZJ5 single colony is picked and streaked on a nitrogen-free medium plate, and whether the strain can grow and form a colony on the nitrogen-free medium is observed.

[0068] Nitrogenase activity determination (acetylene reduction method): Paracoccus marcusii CZJ5 seed liquid is inoculated in LB liquid medium with a 3% inoculation amount, 28℃, 180 rpm, and shaken for 24 h; the culture solution is transferred to a centrifugal tube, centrifuged at 8000 rpm for 10 min at 4℃ to collect the bacterial cells; the bacterial cells are washed with normal saline for 2-3 times and resuspended, and the bacterial cell concentration OD 600 =1.0 is adjusted to prepare a bacterial suspension; 1 mL of the bacterial suspension is added to a centrifugal tube containing 9 mL of nitrogen-free medium for 1 h of reaction and sent to Shanghai Zucaibiotechnology Co., Ltd.; the nitrogenase activity of Paracoccus marcusii CZJ5 of the application is 74.7471 nmol / (mL×h).

[0069] Therefore, the fermentation product of the P. martensii CZJ5 has high nitrogenase activity.

[0070] 2. Phosphorus-dissolving (organic phosphorus) detection experiment

[0071] 5 μL of the seed liquid of the P. martensii CZJ5 was spotted on the center of a King's organic phosphorus detection plate, and three plates were repeated, and then the plates were placed in a 28℃ incubator for 3-5 days, and whether transparent circles were generated around the colonies was observed.

[0072] As shown in Table 1, the P. martensii CZJ5 generated obvious phosphorus-dissolving transparent circles on the organic phosphorus culture medium, indicating that the P. martensii CZJ5 has obvious effects of dissolving organic phosphorus. Figure 4 3. Silicate-dissolving detection experiment

[0073] 5 μL of the seed liquid of the P. martensii CZJ5 was spotted on the center of a silicate-dissolving bacterial culture medium plate, and three plates were repeated, and then the plates were placed in a 28℃ incubator for 3-5 days, and whether oil droplet-like substances were generated around the colonies was observed.

[0074] As shown in Table 2, the P. martensii CZJ5 generated oil droplet-like substances on the silicate-dissolving bacterial culture medium, indicating that the P. martensii CZJ5 has obvious silicate-dissolving properties.

[0075] Figure 5 4. Iron carrier-producing property detection experiment

[0076] 5 μL of the seed liquid of the P. martensii CZJ5 was spotted on the center of a CAS detection culture medium plate, and three plates were repeated, and then the plates were placed in a 28℃ incubator for 3-5 days, and whether orange halos were generated around the colonies was observed.

[0077] As shown in Table 3, the P. martensii CZJ5 generated yellow halos on the iron carrier-producing detection culture medium, indicating that the P. martensii CZJ5 has the property of producing iron carriers.

[0078] Figure 6 In summary, the P. martensii CZJ5 separated by the application has the properties of nitrogen fixation, phosphorus dissolution, silicate dissolution and iron carrier production, can promote the decomposition and conversion of nutrients (nitrogen, phosphorus, silicate and iron) in the soil, and is beneficial to promoting the absorption of nutrients by plants.

[0079] Example 6: P. martensii CZJ5 promotes the growth of wild barley

[0080]

[0081] ​​​Simulation of saline-alkali planting system: adding mixed salt solution in loess culture system to simulate saline-alkali planting environment, and verifying the growth promoting effect of P. maris CZJ5 on wild barley seedling stage.

[0082] (1) The surface of wild barley seeds was sterilized by soaking in 95% alcohol for 2 min, stirring in 1% sodium hypochlorite solution for 3 min, and then washing with sterile water for 10 times. The moisture was maintained, and the seeds were incubated in the dark at 25°C for 2 days. The seeds with a bud length of about 1 cm were selected and sowed.

[0083] (2) The seeds with consistent bud length after incubation were sowed in loess pots with and without bacteria inoculation, with 9 seedlings per treatment. A salt-free system was set as control, and the same bacteria inoculation and non-inoculation treatments were performed. After sowing, the wild barley was cultivated to seedling stage.

[0084] (3) Experimental strain: P. maris CZJ5; LB liquid medium, 28°C, 180 rpm, 36 h of culture; the bacterial cells were obtained by centrifugation at 8000 rpm for 10 min, washed once with physiological saline, and then resuspended. The OD 600 The inoculation amount was 50 mL / pot, and the same amount of salt solution was added every 3 days for 2 times, with the range of 0.6-0.8.

[0085] The wild barley plants irrigated with 50 mL / pot of sterile water were set as control group.

[0086] (4) Salt solutions with salt contents of 0 mmol / L, 200 mmol / L, 400 mmol / L, 600 mmol / L, and 800 mmol / L (NaCl:Na2SO4=1:1) were prepared. After adding the bacterial solution, 50 mL / pot of salt solution was added each time.

[0087] After treatment, the plants were placed in an intelligent greenhouse, and appropriate water was supplemented every 2 days. After 7 days of culture, the plant height, fresh weight, dry weight, and root length of wild barley seedlings were measured to evaluate the effect of P. maris CZJ5 on the growth phenotype of wild barley.

[0088] The results are shown in Figure 7 and Figure 8 According to Figure 7 , under normal conditions (0 mmol / L salt solution), the plant height of wild barley plants treated with CZJ5 (L172) was significantly higher than that of the control group. The wild barley plants in the control group with salt solution concentration greater than 200 mmol / L showed obvious wilting, yellowing, and reduced plant height, while the wild barley plants treated with CZJ5 (L172) had significantly better phenotype than the wild barley plants in the control group with corresponding concentration.

[0089] According to Figure 8It can be seen that under normal conditions (0 mmol / L salt solution) and salt stress conditions, the plant height, root length, fresh weight and dry weight of the wild barley plants treated with CZJ5 (L172) are better than those of the control wild barley plants under the corresponding salt solution concentration.

[0090] The above-described embodiments are merely preferred modes of the present application and are not intended to limit the scope of the present application. Various modifications and improvements to the technical solutions of the present application made by those of ordinary skill in the art without departing from the design spirit of the present application shall fall within the protection scope of the present application as defined by the claims.

Claims

1. A Paracoccus marcusii CZJ5 strain, characterized in that, The Paracoccus martensii CZJ5 has been deposited at the China General Microbiological Culture Collection Center (CGMCC) with accession number CGMCC No. 36255, deposited on October 20, 2025, at the Institute of Microbiology, Chinese Academy of Sciences, No. 3, Courtyard 1, Beichen West Road, Chaoyang District, Beijing.

2. The application of Paracoccus martensii CZJ5 as described in claim 1 in the preparation of a growth-promoting agent to enhance the salt stress tolerance of plants.

3. A growth-promoting agent, characterized in that, The active ingredient is Paracoccus martensii CZJ5 as described in claim 1.

4. The growth-promoting bacterial agent as described in claim 3, characterized in that, The growth-promoting agent has an absorbance of not less than 0.6 at a wavelength of 600 nm.

5. The use of the *Paragonimus westermani* CZJ5 according to claim 1 or the growth-promoting agent according to claim 3 or 4 in any of the following: (1) Desilicates; (2) Iron-producing carrier.

6. The application of the *Paragonimus malathi* CZJ5 as described in claim 1 or the growth-promoting agent as described in claim 3 or 4 in promoting plant growth.

7. A method for promoting plant growth, characterized in that, The method includes the step of applying the *Paracoccus martensii* CZJ5 of claim 1 or the growth-promoting agent of claim 3 or 4 to the plant growth environment.

8. The application of Paracoccus martensii CZJ5 as described in claim 1 or the growth-promoting agent as described in claim 3 or 4 in improving the salt stress tolerance of plants.

9. A method for improving the salt stress tolerance of plants, characterized in that, The method includes the step of applying the *Paracoccus martensii* CZJ5 of claim 1 or the growth-promoting agent of claim 3 or 4 to the plant growth environment.

10. The method as described in claim 9, characterized in that, The plant grows in a saline environment.

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